1. Field of the Invention
The present invention relates to an image processing method and an image processing apparatus, and in particular to an image processing method and an image processing apparatus capable of processing images obtained by a wide-angle optical system correcting a large magnification chromatic aberration.
2. Discussion of the Background Art
Recently, a wide angle imaging apparatus is increasingly demanded as a rear monitor of cars. However, the wider the angle, the larger either a magnification chromatic aberration or a distortion. Thus, the optical system is hardly designed suppressing an aberration. Thus, a performance should be improved by additionally employing image processing. As a conventional technology of correcting an error in an imaging apparatus that employs an optical system having a magnification chromatic aberration and a distortion, the Japanese Patent Application Laid Open No. 2006-345054 describes a method of simultaneously correcting both of the magnification chromatic aberration and the distortion by independently converting a coordinate of each of RGB signals obtained by an imaging element, such as a CCD, a CMOS sensor, etc., per component color of RGB at a later step. Also described is a method of only correcting the distortion by collectively converting respective component colors of RGB at once neglecting the magnification chromatic aberration.
Further, a high band emphasis filter (e.g. MTF correction) is conventionally used for the purpose of correcting deterioration of resolution caused by an optical system, such as a lens, etc.
For example, the Japanese Patent Application Laid Open No. 2006-345054 discusses a method of applying high band emphasis filtering to each of RGB signals per RGB after correcting a magnification chromatic aberration and a distortion of RGB signals. Also discussed there is that RGB signals are separated into brightness and color signals and aberration correction is executed, and then high band emphasis filtering is applied to the brightness signal and the like.
However, the former method introduces a large-scale circuit due to combination of a high band emphasis filter and an aberration correction circuit per each of RGB with poor image quality due to increase of color noise.
The latter method can avoid increase of color noise indeed, but disables correction of the magnification chromatic aberration that is generally enabled by independently correcting an aberration per each of RGB for the purpose of coordinate conversion of brightness and color signals other than RGB signals.